TE-dependence analysis was performed on input data.
A user-defined mask was applied to the data.
An adaptive mask was then generated, in which each voxel's value reflects the number of echoes with 'good' data.
A monoexponential model was fit to the data at each voxel using log-linear regression in order to estimate T2* and S0 maps. For each voxel, the value from the adaptive mask was used to determine which echoes would be used to estimate T2* and S0.
Multi-echo data were then optimally combined using the T2* combination method (Posse et al., 1999).
Principal component analysis based on the PCA component estimation with a Moving Average(stationary Gaussian) process (Li et al., 2007) was applied to the optimally combined data for dimensionality reduction.
The following metrics were calculated: kappa, rho, countnoise, countsigFT2, countsigFS0, dice_FT2, dice_FS0, signal-noise_t, variance explained, normalized variance explained, d_table_score.
Kappa (kappa) and Rho (rho) were calculated as measures of TE-dependence and TE-independence, respectively.
A t-test was performed between the distributions of T2*-model F-statistics associated with clusters (i.e., signal) and non-cluster voxels (i.e., noise) to generate a t-statistic (metric signal-noise_z) and p-value (metric signal-noise_p) measuring relative association of the component to signal over noise.
The number of significant voxels not from clusters was calculated for each component.
Independent component analysis was then used to decompose the dimensionally reduced dataset.
The following metrics were calculated: kappa, rho, countnoise, countsigFT2, countsigFS0, dice_FT2, dice_FS0, signal-noise_t, variance explained, normalized variance explained, d_table_score.
Kappa (kappa) and Rho (rho) were calculated as measures of TE-dependence and TE-independence, respectively.
A t-test was performed between the distributions of T2*-model F-statistics associated with clusters (i.e., signal) and non-cluster voxels (i.e., noise) to generate a t-statistic (metric signal-noise_z) and p-value (metric signal-noise_p) measuring relative association of the component to signal over noise.
The number of significant voxels not from clusters was calculated for each component.
Next, component selection was performed to identify BOLD (TE-dependent), non-BOLD (TE-independent), and uncertain (low-variance) components using the Kundu decision tree (v2.5; Kundu et al., 2013).